Urinary Tract Infection (UTI)

A urinary tract infection (UTI) is an infection that affects a part of the urinary tract. Lower UTIs may involve the bladder (cystitis) or urethra (urethritis) while upper UTIs affect the kidney (pyelonephritis).

Signs and Symptoms

Lower urinary tract infection, also known as a bladder infection, presents with burning during urination and frequent urination. These symptoms can vary from mild to severe and typically last around six days. Some may experience pain above the pubic bone or in the lower back. Upper urinary tract infection, or pyelonephritis, includes flank pain, fever, or nausea and vomiting, often in addition to the symptoms of a lower UTI. Rarely, urine may appear bloody or contain visible pus.

In children, UTIs may present with non-specific symptoms like fever, poor feeding, vomiting, sleepiness, or jaundice. In the elderly, symptoms are often vague, including incontinence, a change in mental status, or fatigue.

Causes and Risk Factors

The most common cause of UTIs is Escherichia coli, responsible for 80–85% of cases. Other bacteria and fungi can also cause UTIs. Risk factors include female anatomy, sexual intercourse, diabetes, obesity, catheterisation, and family history. Women are more prone to UTIs due to their shorter urethra. Sexual activity is a significant risk factor, particularly in young women.

Diagnosis

Diagnosis in young, healthy women can often be based on symptoms alone. In complicated cases or when symptoms are vague, urinalysis and urine culture are used to confirm the diagnosis. Urinalysis looks for urinary nitrites, white blood cells, or leukocyte esterase. A urine culture is considered positive with a bacterial colony count of ≥10³ CFU/mL.

Treatment

Uncomplicated UTIs are treated with a short course of antibiotics such as nitrofurantoin or trimethoprim/sulfamethoxazole. Resistance to these antibiotics is increasing, so in complicated cases, a longer course or intravenous antibiotics may be necessary. Phenazopyridine may help with symptoms, though it is not routinely recommended.

Uncomplicated

Antibiotics like trimethoprim/sulfamethoxazole, nitrofurantoin, or fosfomycin are typically first-line treatments. A three-day course is usually sufficient, though nitrofurantoin requires 5–7 days.

Complicated

These require more aggressive treatment and follow-up. Increased antibiotic resistance is making treatment more challenging. A longer course or intravenous antibiotics is often needed.

Asymptomatic Bacteriuria

Generally, asymptomatic bacteriuria is not treated with antibiotics unless the patient is pregnant, has diabetes, or is undergoing urinary tract procedures likely to cause bleeding. Pregnant women are treated to prevent risks like pyelonephritis, low birth weight, and preterm birth.

Pyelonephritis

Treatments include longer courses of oral antibiotics or intravenous antibiotics. Commonly used antibiotics include ciprofloxacin, trimethoprim/sulfamethoxazole, or amoxicillin/clavulanate. Severe cases may require hospitalisation.

Prognosis

With treatment, symptoms generally improve within 36 hours. However, 15–25% of adults and children may experience chronic symptomatic UTIs, including recurrent infections. Recurrent UTIs are defined as at least two infections in six months or three in twelve months.

Epidemiology

UTIs are the most frequent bacterial infection in women, with 10% affected yearly and 40–60% experiencing an infection at some point in their lives. UTIs occur four times more frequently in females than males. They are also a common cause of hospital-acquired infections, especially in elderly women in care homes.

History

UTIs have been described since ancient times, with the first documented description in the Ebers Papyrus dated to c. 1550 BC. Effective treatment became available with the advent of antibiotics in the 1930s.

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Self-assessment MCQs (single best answer)

Which part of the urinary tract is affected by cystitis?

What is the most common cause of UTIs?

Which symptom is commonly associated with upper urinary tract infection (pyelonephritis)?

What is the typical duration for symptoms of a lower UTI to last?

Which antibiotic is commonly used as a first-line treatment for uncomplicated UTIs?

What is a significant risk factor for developing UTIs, especially in young women?

What is a common finding in urinalysis that suggests a UTI?

In which group is asymptomatic bacteriuria usually treated with antibiotics?

Which historical document contains one of the earliest descriptions of UTIs?

What is the definition of recurrent UTIs?